Metal-to-metal via-type antifuse

ABSTRACT

A metal-to-metal antifuse disposed between two aluminum metallization layers in a CMOS integrated circuit or similar structure includes an antifuse material layer having a substantially aluminum-free conductive link. The substantially aluminum-free link is formed by forming a first barrier metal layer out of TiN having a first thickness, a second barrier metal layer out of TiN having a second thickness which may be less than said first thickness, the first and second barrier metal layers separating the antifuse material layer from first and second electrodes. The antifuse is programmed by applying a voltage potential capable of programming the antifuse across the electrodes with the more positive side of the potential applied to the electrode adjacent the barrier metal layer having the least thickness. In another aspect of the invention, an antifuse having a first barrier metal layer of a first thickness and a second barrier metal layer of a second thickness may be fabricated wherein the first thickness is less than the second thickness and wherein programming of the antifuse is accomplished by placing the more positive voltage of the programming voltage supply on the electrode of the antifuse adjacent the first barrier metal layer.

CROSS-REFERENCE TO RELATED APPLICATION

This is a divisional of patent application Ser. No. 08/538,962, filedOct. 4, 1995, U.S. Pat. No. 5,741,720.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates generally to the field of metal-to-metalantifuses which are used in integrated circuit devices to formselectively programmable conductive links between metallization layersof the integrated circuit devices. More particularly, this inventionrelates to improved antifuses and methods for programming such antifuseswhich yield, after programming, an antifuse link disposed through theantifuse material layer which does not include any significantquantities of aluminum metal and which is, therefore, more reliable andof more predictable resistance.

2. The Prior Art

Antifuses and metal-to-metal antifuses are well known in the art. Aproblem exists, however, which affects the useful life of devicesincorporating metal-to-metal antifuses. Most metal-to-metal antifusesexist between two aluminum metal film metallization layers in anintegrated circuit device such as a CMOS-type device. When a voltage ofsufficient magnitude is applied between the metallization layers in thevicinity of the antifuse, the antifuse material layer and a portion ofthe adjacent metallization layers will disrupt and/or melt or vaporizeand a conductive link will form through the antifuse material layer dueto metal from the adjacent metallization layer being drawn in andintermixed through mass transport and thermal driven material diffusionand chemical reaction, effectively shorting the two metallization layerstogether at the location of the antifuse. The conductive link isprimarily formed of the material in the adjacent metallization layer inthe immediate vicinity of the disruption.

Unfortunately, in many cases it has been noticed that under certaintypes of stress such conductive links will open up or becomenon-conductive. This failure mode often manifests itself after a periodof time during which the antifuse links appear to have been properlyformed. This failure mode is commonly known as "read disturb" becausethe small currents used to read the state of the antifuse--much smallerthan the typical current used to program the antifuse--eventually causea state reversal in the programmed antifuse. Such a failure can destroynot only the particular link that fails, but the entire device in whichthe antifuse is located and, potentially, the equipment in which thedevice is placed. This problem has substantially retarded the commercialacceptance and development of metal-to-metal antifuses.

One factor that is now believed to contribute to read disturb is thepresence of any significant quantity of aluminum in the antifuseconductive links. Aluminum is well known to be subject toelectromigration, i.e., in the presence of an electron current flow, thealuminum metal atoms tend to move along with the electron current flow(opposite to the direction of normal positive to ground electric currentflow). Accordingly, researchers in the prior art have attempted to blockaluminum flow into the antifuse material layer with barrier layers ofvarious materials and various thicknesses. The barrier metals, in turn,have to take the place of the aluminum, and provide essentially theentirety of the conductive material which flows into the antifusematerial layer to form the conductive links that short the twometallization layers together.

During the programming of the antifuse, the resistance between the twometallization layers of the antifuse goes from a few gigaohms to lessthan 100 ohms--a change of over seven orders of magnitude. A relativelylarge amount of heat is also released during this process. This heat, ifnear enough to the aluminum metallization layer, can melt or vaporizeit, making it easy for aluminum to flow into the antifuse material layerto undesirably participate in the formation of conductive links.

One prior art method for forming antifuses is illustrated in FIG. 1.According to this method, an antifuse aperture or via 10 is formedbetween two metallization layers 12, 14 separated by a dielectricmaterial 16 such as SiO₂ ("interlayer dielectric layer"). In this typeof structure, the lower antifuse electrode 18 is formed of an aluminummetallization layer 12 covered by a barrier metal layer 20; the upperantifuse electrode 22 is formed of aluminum metallization layer 14disposed over barrier metal layer 24. Antifuse material layer 26 isdeposited into the antifuse aperture 10 with any of a number oftechniques and may comprise any of a number of materials includingmultiple layers of different materials, and is subject to step coverageproblems which occur whenever a material is deposited into an aperture,namely, a thinning of the deposited layers at the edges or corners ofthe aperture 28, 30 relative to the thickness of the layer at the center32 of the aperture 10. This thinning of both antifuse material layer 26and barrier metal layer 24 tends to force the antifuse to "blow" or"program" in one of the corners 28, 30 at a somewhat unpredictablevoltage and can lead to aluminum from metallization layer 14 breachingthe thinned barrier metal layer 24 to enter antifuse material layer 26during the programming of the antifuse and thereby contaminate theconductive link with aluminum metal.

A similar antifuse structure, known as the "half-stack", is shown inFIG. 2. The FIG. 2 antifuse 34 comprises a lower electrode 36 formed ofan aluminum metallization layer 38 overlaid by a layer of a barriermetal 40. Over the barrier metal layer 40 is disposed an antifusematerial layer 42 which may be of a multi-layer multi-materialconstruction or other construction as is well known in the art. Over theantifuse material layer 42 is an antifuse via 44 through interlayerdielectric layer 52 into which is deposited upper electrode 46 whichconsists of barrier metal layer 48 and aluminum metallization layer 50.An interlayer dielectric layer 52 is disposed between the electrodes 36,46. Such an antifuse may be programmed as follows: provide a firstvoltage pulse across electrodes 36, 46 with the less positive voltagetied to electrode 46 and the more positive voltage tied to electrode 36,the difference between the less positive and more positive voltagesbeing a potential sufficient to program the antifuse, followed by aseries of other voltage pulses, known as an "ac soak" (See, e.g., U.S.patent application Ser. No. 08/110,681 filed Aug. 23, 1993 in the nameof Steve S. Chiang, et al., entitled "Methods For Programming AntifusesHaving at Least One Metal Electrode", which is hereby incorporatedherein by reference), to aid in the formation of the conductive link.This approach of applying the more positive (greater) voltage first tothe bottom electrode is known as "VOB" or voltage on bottom. Theconverse arrangement is known as "VOT" or voltage on top. A method oftenused in programming antifuses is to apply a series of programming pulseshaving an amplitude in one direction greater than the amplitude in theother direction, e.g., +10 volt pulse followed by -8 volt pulse. In thisway, the greater stress is applied during the +10 volt pulse, thus theantifuse is more likely to program during the +10 volt pulse. If itfails to program on the first pulse, it probably won't program on the -8volt pulse and will likely program on a subsequent +10 volt pulse. Inthis way it can be assured that the antifuse will only disrupt while thecurrent is flowing in one particular and predetermined direction.

As used herein, the terms VOT and VOB refer to either a pure DCprogramming voltage, or more commonly, to the first pulse, or to thepulse having the greater magnitude when it is not the first pulse. ThusVOT and VOB refer to the conditions during actual initial formation ofthe conductive link.

When a series of half-stack antifuses having upper barrier layers of TiNof minimum thickness of less than about 2000 Å were programmed in thisfashion, VOB, the results shown in FIG. 3 were obtained FIG. 3 is ahistogram plot showing the resulting resistance of the programmedantifuse along the horizontal axis against the number of antifuseshaving that resistance along the vertical axis. As can be seen, thegrouping is not very tight with an average of 21 ohms, an outlier atnearly 100 ohms and a standard deviation of 3.1. Aluminum content in theconductive links is believed responsible for this relatively poorperformance.

FIG.9A and FIG. 9B are renditions of scanning electron micrographs ofsectioned, programmed antifuses. In FIGS. 9A and FIGS. 9B, antifusescomprising upper aluminum metal layer A, barrier layer B, antifuse layerC, lower barrier layer D and lower aluminum metal layer E are shown. Theantifuse of FIG. 9A was programmed VOT resulting in visibledisruption/mixing of layers D and C but no visible effects to layer B.In this case, a more positive voltage applied to the top electrode (A/B)produces a downward electric current and an upward electron current. Theresult is a conductive filament shorting layers B and D. If thedisruption (shown at "X") of layer D is sufficient to extend all of theway through layer D (which it can be seen that it does not do here),aluminum in layer E will also likely be disrupted/intermixed and thepotential for inclusion of aluminum in the conductive filament issubstantially increased. In FIG. 9B the antifuse was programmed VOB andthe opposite results obtain. Layer D is apparently entirely unscathed,but layers B and C are disrupted. Because such via-type antifuses havewell known step coverage problems, the thickness of layer B is thinnerin the corners of the antifuse aperture, hence the antifuse tends toprogram in the corners due to less overall electrical resistance inthese locations. As can be seen, layer B is significantly eroded to thepoint of almost complete penetration where the antifuse programmed.

U.S. Pat. No. 5,302,546 to Gordon, et al., describes a possible solutionto this problem. In FIG. 1 of Gordon, et al., reproduced here as FIG. 4,an antifuse 54 is shown which incorporates non-conductive spacers 56, 58disposed in the corners 60, 62, respectively, of the antifuse aperture64. These spacers 56, 58 force the conductive metal electrode 66 formedof barrier metal 68 and aluminum metallization layer 70 away from thecorners 60, 62 so that it is disposed immediately above only thethickest part 72 of the antifuse material layer 74. Antifuse 54 isconstructed over a lower electrode 78 which is disposed over dielectriclayer 80 which is in turn disposed over substrate 82. Interlayerdielectric layer 84 separates electrodes 66 and 78. An importantdrawback to this solution is that formation of spacers 56, 58 requiresadditional process steps which increase costs. Gordon, et al. furtherteach using a VOT programming scheme with their antifuse, however, theydo not suggest why this is to be preferred to a VOB scheme, nor do theyteach any utility in providing differential barrier metal layerthicknesses in conjunction with such a scheme or a realization that thespacers 56, 58 may be obviated by choice of materials and programmingtechnique.

Accordingly, it would be extremely desirable to formulate a design for ametal-to-metal via-type antifuse which is not susceptible to conductivelink failure or "read-disturb" as a solution to this problem would openthe door to wide commercial acceptance of metal-to-metal antifuses.

SUMMARY OF THE INVENTION

The present invention solves the problem of conductive link failure inmetal-to-metal via-type antifuses. The solution is essentiallyindependent of antifuse configuration. According to a first aspect ofthe invention, for antifuses including an upper barrier metal layerdisposed in an antifuse via directly over an antifuse material layer,either in, or below the via, the solution is to form the lower barriermetal layer below the via thicker than the upper barrier metal layer inthe via and to provide for programming the antifuse VOT so as to driveelectrons upward through the thinner upper barrier metal layer and intothe overlying aluminum layer during programming. This results in thecreation of an essentially aluminum free conductive link (preferablyless than 1% aluminum content in the link itself). It is highlypreferred to use Titanium Nitride (TiN) as the barrier metal because ofits low thermal conductivity which holds heat in a small region aroundthe rupture caused by blowing the antifuse thus allowing a minimum ofelectrical energy to be used (and deposited in the antifuse) and becauseof its high resistance to aluminum diffusion through it which furtherminimizes the likelihood of disrupting/intermixing aluminum andpreventing aluminum from diffusing through the TiN which could then forma part of the conductive link of the programmed antifuse.

According to a second aspect of the invention, an antifuse having afirst barrier metal layer of a first minimum thickness and a secondbarrier metal layer of a second minimum thickness may be fabricatedwherein the first minimum thickness is less than the second minimumthickness and wherein programming of the antifuse is accomplished byplacing the more positive voltage of the programming voltage supply onthe electrode of the antifuse adjacent the first (thinner) barrier metallayer.

According to a third aspect of the present invention, it is possible tofabricate reliable antifuses having upper and lower TiN barrier metallayers surrounding an antifuse material layer and adjacent to aluminummetallization layers with one barrier metal layer thinner than theother, and having a minimum thickness of as little as 1000 Å by applyingthe programming signal as follows: (I) where the upper barrier layer hasa minimum thickness in the range of 1000 Å-2000 Å and the lower barrierlayer has a minimum thickness in the range of 2000 Å or more, using VOTprogramming to take advantage of the thicker lower barrier layer toprotect the antifuse filament from aluminum incursion and (II) where theupper barrier layer has a minimum thickness in the range of 2000 Å ormore and the lower barrier layer has a minimum thickness in the range of1000 Å-2000 Å, using VOB programming to take advantage of the thickerupper barrier layer to protect the antifuse filament from aluminumincursion.

According to a fourth aspect of the present invention, it is possible tofabricate reliable antifuses having upper and lower TiN barrier metallayers both exceeding 2000 Å in minimum thickness surrounding anantifuse material layer and adjacent to aluminum metallization layerswith by applying the programming signal as follows: using either VOT orVOB programming as the thick barrier layers will protect the antifusefilament from aluminum incursion.

OBJECTS AND ADVANTAGES OF THE INVENTION

Accordingly, it is an object of the present invention to providemetal-to-metal via-type antifuses which are not subject to conductivelink failure.

It is a further object of the present invention to provide a programmedantifuse structure having a conductive link formed therein lacking anysignificant amount of aluminum metal.

It is a further object of the present invention to provide improvedmetal-to-metal via-type antifuse structures.

Yet a further object of the present invention is to provide improvedprogramming methods for use with metal-to-metal via-type antifusestructures which result in programmed antifuses having increased lifeand reliability.

These and many other objects and advantages of the present inventionwill become apparent to those of ordinary skill in the art from aconsideration of the drawings and ensuing description of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS AND PHOTOGRAPHS

FIG. 1 is a cross sectional diagram of a prior art antifuse.

FIG. 2 is a cross sectional diagram of an antifuse.

FIG. 3 is a histogram of resistance vs. quantity for a series of testsrun with antifuses fabricated according to FIG. 2.

FIG. 4 is a cross sectional diagram of a prior art antifuse.

FIG. 5 is a cross sectional diagram of an antifuse structure accordingto a presently preferred embodiment of the present invention.

FIG. 6 is an enlargement of a portion of FIG. 5 additionally showing aconductive link formed according to a presently preferred embodiment ofthe present invention.

FIG. 7 is a histogram of resistance vs. quantity for a series of testsrun with antifuses fabricated according to a presently preferredembodiment of the present invention.

FIG. 8 is a schematic diagram of a typicalmetal/barrier/antifuse/barrier/metal antifuse structure.

FIG. 9A is a rendition of a scanning electron micrograph of a sectioned,programmed antifuse which was programmed VOT.

FIG. 9B is a rendition of a scanning electron micrograph of a sectioned,programmed antifuse which was programmed VOB.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Those of ordinary skill in the art will realize that the followingdescription of the present invention is illustrative only and is notintended to be in any way limiting. Other embodiments of the inventionwill readily suggest themselves to such skilled persons from anexamination of the within disclosure.

The preferred embodiment described herein is for an antifuse having anantifuse aperture of diameter approximately 10000 Å or less andprogrammable with an applied potential preferably in the range of about9.5 V to about 12 V at a programming current of about 10-30 mA. Changesin the programming voltage will scale with changes in dimension andantifuse material(s) choice as known to those of ordinary skill in theart.

One of the main purposes for developing metal-to-metal antifuses is sothat they may be disposed over an active region of a semiconductorsubstrate which has transistors formed in it. In this way, the "realestate" taken by the transistors is reused by the antifuses, much theway as a sky scraper is able to reuse the same land with each additionalfloor thus increasing areal building density. The ability to safelyplace antifuses over an active region of a semiconductor substratedepends upon the ability of the antifuses to behave in a manner before,during and after programming that does not result in contamination orother damage to the transistors already constructed in the activeregion.

It is thus desirable to program the antifuses with a minimum energy sothat a minimum heating of the aluminum metallization layer is achievedthus minimizing the likelihood that aluminum will migrate into theactive transistor region of the semiconductor substrate as well as intothe conductive links of the antifuse itself. According to a presentlypreferred embodiment of the present invention, the structure of FIG. 5is capable of meeting these requirements. Referring to FIG. 5, andbeginning at the bottom, the layers are: active transistor region 86;insulating layer 88 (thickness range of about 5000-15000 Å with about7500 Å presently preferred, preferred material(s): SiO₂); barrier metallayer 90 (thickness range of about 100-1000 Å with about 500 Å presentlypreferred, preferred material(s): Ti adhesion layer of thickness about100-500 Å (preferably about 250 Å) under a TiN barrier layer ofthickness about 100-500 Å (preferably about 250 Å)); first metallizationlayer or "Metal-1" 92 (thickness range of about 5000-15000 Å with about8000 Å presently preferred), interlayer dielectric 94 (thickness rangeof about 5000-15000 Å with about 7500 Å presently preferred, preferredmaterial(s): SiO²); second metallization layer or "Metal-2" 96(thickness range of about 5000-15000 Å with about 8000 Å presentlypreferred); another barrier metal layer 98 (thickness range of about1000-4000 Å with about 2000 Å presently preferred); interlayerdielectric 100 (thickness range of about 4000-15000 Å with about 7500 Åpresently preferred, preferred material(s): SiO₂); antifuse aperture 102(preferably round in shape with a depth in the range of about 3000-14000Å with about 6500 Å presently preferred, and a diameter of about3000-15000 Å with about 10000 Å presently preferred); antifuse materiallayer 104 (thickness range 300-1500 Å with the followingmaterials/thicknesses choices presently preferred: (1) SiN/amorphousSi/SiN in a thickness ratio of 75 Å:500 Å:75 Å,Å) (2) SiN/amorphous Siin a thickness ratio of 150 Å:500 Å, (3) amorphous silicon of thicknessabout 1000 Å or (4) SiN of thickness about 300 Å, barrier metal layer106 (thickness range of about 1000-4000 Å) disposed in antifuse aperture102; and, finally, third metallization layer of "Metal-3" 108 (thicknessrange of about 5000-15000 Å, with about 8000 Å presently preferred). Ina standard CMOS process, as envisioned here, the three metallizationlayers 92, 96 and 108 are all fabricated of an aluminum alloy in aconventional and well-known manner.

FIG. 6 is an enlarged portion of FIG. 5 showing a conductive antifuselink 110 formed in antifuse material layer 104 shorting barrier metallayer 98 to barrier metal layer 106.

According to the present invention, TiN is highly preferred for thebarrier metal layers 98 and 106. TiN is a very poor thermal conductor,unlike Titanium Tungsten (TiW) which is often used as a barrier metal.TiN's thermal conductivity is 0.291 Wcm⁻¹ K⁻¹. Because TiN acts, inessence, as a thermal insulator, it is preferred in this application asfollows: when a voltage is applied between Metal-2 and Metal-3 ofsufficient magnitude to blow antifuse material layer 104, great amountsof thermal energy will be released as evidenced by FIG. 9A and FIG. 9Bdiscussed above. If barrier metal layers 98 and 106 had a high thermalconductivity, they would rapidly conduct away the heat released inblowing the antifuse 104 with two results: first, it would simply takemore energy to disrupt/intermix enough of barrier metal layers 98 and106 to form the conductive links bridging antifuse material layer 104;and second, this additional energy would be likely to result in meltingand/or vaporization of Metal-2 and/or Metal-3, freeing up aluminum sothat it can participate in link formation within antifuse material layer104. This is highly undesirable because, as discussed above, aluminum issubject to electromigration and its presence in any significant quantity(i.e., more than 1%) within these conductive links may result in anunacceptably high probability of read disturb in programmed antifusesand, thus, the failure of the device.

While one might thus seek to coat all antifuses with copious layers ofTiN, a practical limitation on the use of TiN in this application isthat it is difficult to put an arbitrarily large thickness of TiN withinan aperture in a conventional CMOS-type fabrication process. Forcircular apertures of diameter approximately 1.0 μm (10000 Å), or less,as presently preferred, it is convenient to deposit a layer of TiN ofapproximately 1000 Å thickness (at the edge of the aperture which mayrequire that up to about 3000 Å be deposited-due to step coverage-causedthinning at the edges within such an aperture). This thickness at theedge may be stretched to approximately 2000 Å thickness at increasedcost and throughput, and significantly thicker films are difficult toachieve with TiN in an aperture using available technology. Accordingly,to take advantage of TiN's desirable properties (good barrier metal andpoor thermal conductor), one is practically limited by the availablemanufacturing processes to a film thickness of 1000 Å-2000 Å at the edgewith the thinner film thickness preferred for manufacturability reasons.This desire for thinner films of TiN is in direct conflict with theopposite desire discussed above to deposit as much TiN as possible inthe aperture to protect against inadvertent breakthrough of aluminummetal into either the antifuse material layer or, potentially, lowerlevels of the semiconductor device such as the active transistor region.

Referring now to FIG. 8, a schematic diagram of an antifuse fabricatedaccording to the present invention is shown. In FIG. 8, the antifuse 112has a lower aluminum metallization layer 114 covered by a lower TiNbarrier layer 116 of minimum thickness BB. Over layer 116 is disposedantifuse material layer(s) 118 which may be of any desired constructionincluding multi-layer multi-material construction as known in the art.Through antifuse material layer 118 is disposed conductive antifusefilament 124 shown schematically as a jagged line. Over antifuse layer118 is upper TiN barrier layer 120 of minimum thickness AA and over thatis upper metallization layer 122 of aluminum.

According to the present invention, it is now possible to fabricatereliable antifuses with one barrier metal layer thinner than the other,and having a thickness of as little as 1000 Å by applying theprogramming signal as follows: (I) where the upper barrier layer 120 hasa minimum thickness AA in the range of 1000 Å-2000 Å and lower barrierlayer 116 has a minimum thickness BB in the range of 2000 Å or more, VOTprogramming as in FIG. 9A will take advantage of the thicker lowerbarrier layer to protect the antifuse filament 124 from aluminumincursion; (II) where the upper barrier layer 120 has a minimumthickness AA in the range of 2000 Å or more and lower barrier layer 116has a minimum thickness BB in the range of 1000 Å-2000 Å, VOBprogramming as in FIG. 9B will take advantage of the thicker upperbarrier layer to protect the antifuse filament 124 from aluminumincursion; (III) where the upper barrier layer 120 has a minimumthickness AA of more than about 2000 Å and lower barrier layer 116 has aminimum thickness BB of more than about 2000 Å, either VOT or VOBprogramming can be used as the thick barrier layers will protect theantifuse filament 124 from aluminum incursion in any event.

This technique assures that the more positive voltage side (as opposedto ground or the less positive voltage side) of the first (or only)pulse is applied to the side of the antifuse having the thinnest layerof TiN barrier metal. In this way, the electron current (opposite thedirection of the electric current) flows toward the more positiveterminal, thus, the thinner barrier metal at the more positive terminalis not likely to allow the release of aluminum into the antifusematerial layer because the electron flow toward the aluminum will causeany flow of aluminum to be away from the antifuse material layer, andsince less disruption occurs to the low potential material, the TiN willretain enough material to prevent aluminum diffusion at some later timeduring chip operational lifetime.

Referring now to FIG. 7, a histogram much like that of FIG. 3 is shown.In this case, the devices were programmed "VOT" rather than "VOB" as inFIG. 3. The result is a much tighter distribution with no outliers, anaverage programmed antifuse resistance of 20 ohms, and a standarddeviation of 1.25. The antifuse design of FIG. 7 incorporated a lowerTiN barrier layer having a thickness of 2000 Å or more and an upper TiNbarrier layer having a thickness in the range of about 1000 Å-2000 Å.

Accordingly, a large class of antifuse structures have been shown whichcan be programmed as described to provide substantially aluminum-freeconductive links. Such antifuse structures will not suffer from readdisturb due to aluminum contamination and will provide stable reliablemetal-to-metal antifuses for use in semiconductor devices.

While illustrative embodiments and applications of this invention havebeen shown and described, it would be apparent to those skilled in theart that many more modifications than have been mentioned above arepossible without departing from the inventive concepts set forth herein.The invention, therefore, is not to be limited except in the spirit ofthe appended claims.

What is claimed is:
 1. A programmed antifuse disposed in an integratedcircuit comprising:a lower conductive layer formed of a film of materialincluding aluminum; a lower barrier metal layer disposed over and inelectrical contact with said lower conductive layer, said lower barriermetal layer formed of TiN and having a first minimum thickness ofgreater than 2000 Å; an antifuse material layer disposed over and incontact with said lower barrier metal layer; an upper barrier metallayer disposed over and in contact with said antifuse material layer,said upper barrier metal layer formed of TiN and having a second minimumthickness, said second minimum thickness being in the range of 1000Å-2000 Å; an upper conductive layer formed of a film of materialincluding aluminum, said film disposed over and in electrical contactwith said upper barrier metal layer; and a conductive link locatedwithin said antifuse material layer and electrically connecting saidlower barrier metal layer and said upper barrier metal layer, saidconductive link comprising substantially no aluminum metal.
 2. Aprogrammed antifuse according to claim 1 wherein said conductive linkcomprises less than 1% aluminum by weight.
 3. A programmed antifusecomprising:a lower electrode formed of a film of material includingaluminum; a lower barrier metal layer disposed over and in electricalcontact with said lower conductive layer, said lower barrier metal layerformed of TiN and having a first minimum thickness in the range of 1000Å to 2000 Å; an antifuse material layer disposed over and in contactwith said lower barrier metal layer; an upper barrier metal layerdisposed over and in contact with said antifuse material layer, saidupper barrier metal layer formed of TiN and having a second minimumthickness, said second minimum thickness being at least 1000 Å and saidfirst minimum thickness being greater than said second thickness; anupper electrode formed of a film of material including aluminum, saidfilm disposed over and in electrical contact with said upper barriermetal layer; and a conductive link located within said antifuse materiallayer and electrically connecting said lower barrier metal layer andsaid upper barrier metal layer, said conductive link comprisingsubstantially no aluminum metal.
 4. A programmed antifuse according toclaim 3 wherein said conductive link comprises less than 1% aluminum byweight.
 5. An antifuse comprising:a lower conductive layer formed of afilm of material including aluminum; a lower barrier metal layerdisposed over and in electrical contact with said lower conductivelayer, said lower barrier metal layer formed of TiN and having a firstminimum thickness of greater than 2000 Å; an antifuse material layerdisposed over and in contact with said lower barrier metal layer; anupper barrier metal layer disposed over and in contact with saidantifuse material layer, said upper barrier metal layer formed of TiNand having a second minimum thickness, said second minimum thicknessbeing in the range of 1000 Å-2000 Å; an upper conductive layer formed ofa film of material including aluminum, said film disposed over and inelectrical contact with said upper barrier metal layer; and programmingmeans for programming the antifuse, said programming means including apower supply capable of applying:a first programming signal between saidlower conductive layer and said upper conductive layer for a firstperiod of time, a voltage induced on said upper conductive layerreferenced to said lower conductive layer being positive; a secondprogramming signal between said lower conductive layer and said upperconductive layer for a second period of time after said first period oftime, a voltage induced on said lower conductive layer referenced tosaid upper conductive layer being negative and the amplitude of saidvoltage being less than the amplitude of said voltage applied in saidfirst programming signal; a third programming signal for a third periodof time after said second period of time, said third programming signalequivalent to said first programming signal; and a fourth programmingsignal for a fourth period of time after said third period of time, saidfourth programming signal equivalent to said second programming signal.6. An antifuse comprising:a lower conductive layer formed of a film ofmaterial including aluminum; a lower barrier metal layer disposed overand in electrical contact with said lower conductive layer, said lowerbarrier metal layer formed of TiN and having a first minimum thicknessin the range of 1000 Å-2000 Å; an antifuse material layer disposed overand in contact with said lower barrier metal layer; an upper barriermetal layer disposed over and in contact with said antifuse materiallayer, said upper barrier metal layer formed of TiN and having a secondminimum thickness, said second minimum thickness being greater than 2000Å; an upper conductive layer formed of a film of material includingaluminum, said film disposed over and in electrical contact with saidupper barrier metal layer; and programming means for programming theantifuse, said programming means including a power supply capable ofapplying:a first programming signal between said lower conductive layerand said upper conductive layer for a first period of time, a voltageinduced on said upper conductive layer referenced to said upperconductive layer being positive; a second programming signal betweensaid lower conductive layer and said upper conductive layer for a secondperiod of time after said first period of time, a voltage induced onsaid upper conductive layer referenced to said upper conductive layerbeing negative and the amplitude of said voltage being less than theamplitude of said voltage applied in said first programming signal; athird programming signal for a third period of time after said secondperiod of time, said third programming signal equivalent to said firstprogramming signal; and a fourth programming signal for a fourth periodof time after said third period of time, said fourth programming signalequivalent to said second programming signal.
 7. An antifuse accordingto claim 1 disposed in a semiconductor device over an active transistorregion.
 8. An antifuse according to claim 2 disposed in a semiconductordevice over an active transistor region.
 9. An antifuse according toclaim 3 disposed in a semiconductor device over an active transistorregion.
 10. An antifuse according to claim 4 disposed in a semiconductordevice over an active transistor region.
 11. An antifuse according toclaim 5 disposed in a semiconductor device over an active transistorregion.
 12. An antifuse according to claim 6 disposed in a semiconductordevice over an active transistor region.
 13. An unprogrammed antifusedisposed in an integrated circuit comprising:a lower conductive layerformed of a film of material including aluminum; a lower barrier metallayer disposed over and in electrical contact with said lower conductivelayer, said lower barrier metal layer formed of TiN and having a firstminimum thickness of greater than 2000 Å; an antifuse material layerdisposed over and in contact with said lower barrier metal layer; anupper barrier metal layer disposed over and in contact with saidantifuse material layer, said upper barrier metal layer formed of TiNand having a second minimum thickness, said second minimum thicknessbeing in the range of 1000 Å-2000 Å; an upper conductive layer formed ofa film of material including aluminum, said film disposed over and inelectrical contact with said upper barrier metal layer; and saidunprogrammed antifuse designed to be programmed by applying aprogramming signal between said lower conductive layer and said upperconductive layer, a voltage induced on said lower conductive layerreferenced to said lower conductive layer being positive, such that saidprogramming signal induces metal from said lower barrier metal later andsaid upper barrier metal later into said antifuse material layer,forming a conductive link between said lower barrier metal layer andsaid upper barrier metal layer, said conductive link containingsubstantially no aluminum.
 14. An unprogrammed antifuse disposed in anintegrated circuit comprising:a lower conductive layer formed of a filmof material including aluminum; a lower barrier metal layer disposedover and in electrical contact with said lower conductive link, saidlower barrier metal layer formed of TiN and having a first minimumthickness in the range of about 1000 Å to about 2000 Å; an antifusematerial layer disposed over and in contact with said lower barriermetal layer; an upper barrier metal layer disposed over and in contactwith said antifuse material layer, said upper barrier metal layer formedof TiN and having a second minimum thickness of greater than 2000 Å; andan upper conductive layer formed of a film of material includingaluminum, said film disposed over and in electrical contact with saidupper barrier metal layer; and said unprogrammed antifuse designed to beprogrammed by applying a programming signal between said lowerconductive layer and said upper conductive layer, a voltage induced onsaid lower conductive layer referenced to said upper conductive layerbeing positive, such that said programming signal induces metal fromsaid lower barrier metal later and said upper barrier metal later intosaid antifuse material layer, forming a conductive link within saidantifuse material layer electrically connecting said lower barrier metallayer and said upper barrier metal layer, said conductive linkcontaining substantially no aluminum.
 15. An unprogrammed antifusedisposed in an integrated circuit comprising:a lower conductive layerformed of a film of material including aluminum; a lower barrier metallayer disposed over and in electrical contact with said lower conductivelayer, said lower barrier metal layer formed of TiN and having a firstminimum thickness of at least about 2000 Å; an antifuse material layerdisposed over and in contact with said lower barrier metal layer; anupper barrier metal layer disposed over and in contact with saidantifuse material layer, said upper barrier metal layer formed of TiNand having a second minimum thickness greater than 2000 Å, said secondminimum thickness being greater than said first minimum thickness; andan upper conductive layer formed of a film of material includingaluminum, said film disposed over and in electrical contact with saidupper barrier metal layer; and said unprogrammed antifuse designed to beprogrammed by applying either (1) a programming signal between saidlower conductive layer and said upper conductive layer, a voltageinduced on said lower conductive layer referenced to said lowerconductive layer being positive, such that said programming signalinduces metal from said lower barrier metal later and said upper barriermetal later into said antifuse material layer, forming a conductive linkbetween said lower barrier metal layer and said upper barrier metallayer, said conductive link containing substantially no aluminum, or (2)a programming signal between said lower conductive layer and said upperconductive layer, a voltage induced on said lower conductive layerreferenced to said upper conductive layer being positive, such that saidprogramming signal induces metal from said lower barrier metal later andsaid upper barrier metal later into said antifuse material layer,forming a conductive link within said antifuse material layerelectrically connecting said lower barrier metal layer and said upperbarrier metal layer, said conductive link containing substantially noaluminum.
 16. A programmed antifuse according to claim 5 wherein saidconductive link comprises less than 1% aluminum by weight.
 17. Aprogrammed antifuse according to claim 6 wherein said conductive linkcomprises less than 1% aluminum by weight.
 18. A programmed antifuseaccording to claim 11 wherein said conductive link comprises less than1% aluminum by weight.